The Universe, Solar System, and Planets I

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The Universe, Solar System, and Planets I
Questions How do we know the Big Bang
happened? How do we know the Universe is
expanding? What is the timeframe of Universe
evolution?
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News Flash NASA/CNN report first stars formed
early than once thought
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Edwin Hubble at Mt. Wilson
Hubbles observations at the 100 inch during
the 1920s led him to the conclusion that the
universe is expanding, and that an objects
recession velocity is proportional to its
distance from the observer.
Hubble guiding the Hooker 100 inch telescope in
1923.
The Hooker 100 inch telescope atop Mt.
Wilson near Pasadena, CA. It was the largest
telescope in the world from 1917-1947.
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Deep Hubble Space Telescope Image
A deep image of an empty portion of the sky
with the Hubble Space Telescope reveals that the
universe is filled with galaxies- many just like
our own. The light we see from the most
distant galaxies has traveled approx- imately 10
billion years to reach us.
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Using the Doppler Effect to Measure Velocity
Redshift
Blueshift
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Galaxy Spectroscopy

• Spectra of a nearby star and a distant galaxy
• Star is nearby, approximately at rest
• Galaxy is distant, traveling away from us at
  12,000 km/s

Stellar Spectrum
Sodium
Magnesium
Galaxy Spectrum
Calcium
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Origin of the Universe -Did It Begin with a Big
Bang?
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Discovery of the Background Radiation from
initial Big Bang -Long wavelength -came from
all directions
Penzias and Wilson, 1965
Arecibo Dish, Puerto Rico
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Early History of the Universe

• Matter as we know it did not exist at the time of
  the Big Bang, only pure energy. Within one
  second, the 4 fundamental forces were separated
• gravity - the attraction of one body toward
  another
• electromagnetic force - binds atoms into
  molecules, can be transmitted by photons
• strong nuclear force - binds protons and neutrons
  together in the nucleus
• weak nuclear force - breaks down an atoms
  nucleus, producing radioactive decay

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Early History of the Universe

• After 3 minutes, photons and neutrons began to
  fuse to form the nuclei of hydrogen and helium
  atoms
• About 300,000 years later, temperatures were cool
  enough for complete hydrogen and helium atoms to
  form
• Photons escaped from matter about the same time,
  and light existed for the first time

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Changing Composition of the Universe

• 200 million years later, with expansion still
  occurring, stars and galaxies began forming from
  leftover matter - hydrogen and helium
• nuclear fusion in stars has reduced the original
  composition of 100 H and He to 98
• when a dying star explodes, the heavier elements
  created by fusion are blown into space to be
  recycled by newly forming stars
• the overall composition of the galaxies is
  gradually changing to the heavier elements

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The Solar System - Its Origin and Early
Development

• Our solar system, part of the Milky Way galaxy,
  consists of the Sun, nine planets, 64 known
  moons, many asteroids, millions of comets and
  meteorites, as well as interplanetary dust and
  gases

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The Solar System - Its Origin and Early
Development
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General Characteristics of the Solar System

• Planetary orbits and rotation
• planet and satellite orbits are in a common plane
• nearly all planet and satellite orbital and spin
  motions are in the same direction
• rotation axes of nearly all planets and
  satellites are roughly perpendicular to the plane
  of the ecliptic

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General Characteristics of the Solar System

• Chemical and physical properties of the planets
• the terrestrial planets are small, have a high
  density, and are composed of rock and metallic
  elements
• the Jovian planets are large, have a low density,
  and are composed of gases and frozen compounds

• Slow rotation of the Sun
• Interplanetary material
• existence and location of asteroid belt
• distribution of interplanetary dust

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Meteorites - Visitors from Outer Space

• Meteorites are believed to be pieces of material
  that originated in the formation of the Solar
  System about 4.6 billion years ago

• Stones - composed of iron and magnesium
  silicates, about 93 of all meteorites
• Irons - composed of iron and nickel alloys
• Stony-Irons - nearly equal amounts of iron and
  nickel and silicate minerals